This invention relates to a method of brominating substituted anilines. In particular, it relates to a method in which a substituted aniline is brominated in water in the absence of any acid.
4-Trifluoromethoxy-2,6-dibromoaniline (TFMDBA) is used to make herbicides and other chemicals. It can be made by reacting 4-aminotrifluoromethoxy benzene (TFMB) with bromine in a solution of 10 times acetic acid and 2 equivalents of sodium acetate. (See U.S. Pat. No. 5,045,554, column 5, line 62, to column 6, line 3.) The large amount of acetic acid that that reaction requires is expensive for an industrial process.
It is also known that 2,4,6-tribromo aniline can be made by reacting aniline with bromine in 50 times water containing about 1 equivalent of hydrochloric acid. (See Organic Synthesis, Wiley; New York, 1943; collected vol. II, pages 592 to 594.) The hydrochloric acid is used to prevent the formation of the bromide salt, which would remain in solution, while 2,4,6-tribromo aniline is insoluble in water and precipitates.